82 BRITISH AVONIAN CONODONT FAUNAS 
In outer lateral view the unit is characterized by a rather straight median portion 
of more or less even depth, both the oral surface and to a lesser extent the aboral 
surface appearing straight-edged in lateral view. The basal apron of the outer 
lateral margin is considerably less flared and deep than that on the opposite lateral 
margin. 
The anterior blade decreases rapidly in depth anteriorly and its aboral edge, though 
straight, is depressed vertically. It bears about six oral denticles, of which only 
the most posterior are conspicuous, the largest being the most posterior of the 
series. The oral edge is bluntly crenulate and the whole outer lateral face is gently 
convex or flat, the junction with the aboral edge below the main denticle being 
concave. The posterior end of the unit is gently downflexed and the posterior aboral 
terminus is bluntly spatulate in lateral view. 
The posterior platform decreases in width towards the posterior end, the decrease 
being especially prominent in its posterior quarter. The anterior edge of the 
anterior blade falls sharply away in its anterior third, so that the anterior is vertical, 
but is still minutely denticulate. In inner lateral view the most prominent feature 
is the large, rounded, depressed apron above the aboral margin of the cavity. This 
occupies about half the total length of the unit and is regularly and strongly convex. 
In aboral view the cavity is also a conspicuous feature. The anterior half is wider 
than the posterior, the anterior point of origin being below the apical denticle. The 
point of maximum width is about one-third of the total length from the anterior end 
and the cavity is terminated posteriorly about five-sixths of the total length of the 
unit from the anterior end, so that the posterior aboral edge of the unit is blade-like. 
The anterior aboral edge of the blade is also thin. 
Cavusgnathus unicornis Youngquist & Miller 
Plate 31, figs. 13a, b 
1949 Cavusgnathus unicornis Youngquist & Miller : 619, Pl. ror, figs. 18-23. 
1947 Cavusgnathus cristata Cooper (partim) : 91, Pl. 20, figs. 7-10 only. 
1957 Cavusgnathus unicornis Youngquist & Miller ; Rexroad : 17, Pl. 1, fig. 7. 
1957 ? Cavusgnathus unicornis Youngquist & Miller ; Lys & Serre : 1042, Pl. 2, figs. 3a, b. 
1958 Cavusgnathus unicornis Youngquist & Miller ; Rexroad: 17, Pl. 1, figs. 6-11. 
1961 Cavusgnathus unicornis Youngquist & Miller; Rexroad & Burton: 1152, Pl. 138, 
figs. 10-12. 
1961 Cavusgnathus unicoynis Youngquist & Miller ; Rexroad & Collinson: Pl. 1. 
1963 Cavusgnathus unicorynis Youngquist & Miller; Rexroad & Collinson: 4g, Pl. 1, figs. 
26-27. 
1964 Cavusgnathus unicornis Youngquist & Miller ; Rexroad & Furnish : 670, Pl. 111, fig. 6. 
1965 Cavusgnathus unicornis Youngquist & Miller ; Rexroad & Nicoll : 18, Pl. 1, figs. 18-20. 
MATERIAL. 131 specimens: figured, X 329. 
Rance. North Crop CYD 6-3D 14/15, Avon Gorge C 34—-D 26. 
DESCRIPTION. The most distinctive feature of this species is the conspicuously 
large posterior denticle of the anterior blade. 
In aboral view the cavity is a conspicuous feature of the unit. It tends to be 
